Quick Answer
ATS sizing is more critical than installation quality because a properly sized ATS is the backbone of a reliable and efficient power system, while a well-installed ATS can still function but with reduced capacity and lifespan.
ATS Sizing Fundamentals
ATS (Automatic Transfer Switch) sizing is critical to ensure that the load can be safely and efficiently transferred between the grid and generator sources. A correctly sized ATS takes into account the total load, the generator’s capacity, and the voltage drop between the ATS, generator, and critical load equipment. For example, a 20 kW generator can supply a 15 kW load with some headroom for startup and inrush currents, but a 25 kW load would be too high and may cause overloading, overheating, and premature failure of the ATS.
Understanding Electrical Codes and Standards
Electrical safety codes and standards, such as the National Electric Code (NEC), dictate the minimum requirements for ATS installation and sizing. For instance, NEC 702.9 requires that the ATS be sized to handle the maximum load, including motor starting currents, which can be up to 6 times the motor’s rated current. In addition, the NEC requires that ATS installations be designed and installed by qualified electricians or engineers to ensure compliance with the applicable codes and standards.
Installing the Right ATS
When selecting an ATS for a specific application, it’s essential to consider the load types, the generator’s characteristics, and the electrical safety codes and standards that apply. For example, a load with a high startup current, such as a compressor or a pump, may require a larger ATS with a higher interrupting capacity to handle the inrush current. A qualified electrician or engineer should be consulted to ensure that the ATS is properly sized and installed to meet the specific requirements of the application.
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